ИСТИНА

We report on the synthesis, characterization, and self-organization of Janus micelles, Janus cylinders, and amphiphilic block and graft copolymers. Janus micelles are surface-compartmented nanoparticles with a polystyrene (PS) and a poly(methacrylic acid) (PMAA) hemisphere. They were prepared in a three-step procedure: first polystyrene-block-polybutadiene-block-poly(methyl methacrylate) (SBM) block terpolymers were made by sequential anionic polymerization, then the polybutadiene center blocks were cross-linked in an "ls" bulk morphology with polybutadine (PB) spheres between PS and PMMA lamellae. Finally the ester groups of the PMMA segments were hydrolyzed to form PS-PB-PMAA Janus micelles. These micelles show spherical supermicelles and even larger structures in aqueous solution, as demonstrated by fluorescence correlation spectroscopy, field-flow fractionation, static and dynamic light scattering, cryo-TEM, SEM, and AFM. Janus cylinders were prepared by crosslinking the PB center blocks of SBM block terpolymers in an "lc" bulk morphology with PB cylinders between PS and PMMA lamellae. Due to their enormous molecular weight and due to cylinder interconnections at grain boundaries the PS-PB-PMMA Janus cylinders are insoluble. Sonification renders single cylinders with lengths between 200 nm and > 100 µm (AFM, SFM), depending on the ultrasound energy. The hydrolysis of the PMMA segments is under way. We have investigated the effect of polymer topology on the aggregation behaviour in aqueous solution of amphiphilic diblock and graft copolymers of n-butyl acrylate (nBA) and acrylic acid (AA). For this end we synthesized diblock and graft copolymers of nBA and tert-butyl acrylate (tBA) of different chemical compositions using controlled radical polymerization (ATRP), followed by hydrolysis of the tert-butyl groups. The micellisation of these amphiphilic copolymers was studied by tensiometry, fluorometry, DLS, SANS, AFM, and cryo-TEM. Besides a strong pH dependence, it is shown that graft copolymers have a weaker tendency to form micelles than block copolymers. We assume that the stabilization of unimers by many short hydrophilic side chains is easier than by a single long hydrophilic block.